The invention relates to a largely temperature stable electronic switch for use as the input member of a circuit for converting a pulse signal into a continuous analog signal having an amplitude representative of the duty cycle of the pulse signal. For the purpose of conversion, pulse signals are supplied to an electronic switch, the pulses having a pulse duration .tau. and a period duration T. The electronic switch connects a d.c. voltage U to an integrating element, controlled by these pulses, at the output of which element an analog signal U.sub.M with the size EQU U.sub.M =(.tau./T).multidot.U
is obtained.
For certain applications, e.g. for the purpose of producing a tuning d.c. voltage for electronic tuners in television devices, the analog signal U.sub.M must be varied in relatively small steps; in this example the steps are 1/10 000th of the d.c. voltage U. As a result of integrated circuit technology, the minimum pulse duration .tau. is, for example, 5 .mu.sec. For stability of the analog signal U.sub.M in relation to the temperature demands ##EQU1## are made within an operating temperature range of 20.degree. . . . 50.degree. C. so that the pulse duration .tau. may not vary within the stated temperature range more than 1/1000th .tau. corresponding to .DELTA..tau.=5 nsec. This makes extremely high demands on temperature stability of the electronic switch.